/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.hadoop.hbase;
  
  import java.io.IOException;
  import java.util.ArrayList;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.util.Shell.ExitCodeException;
  import org.apache.hadoop.util.Shell.ShellCommandExecutor;
  
  /**
   * A utility for executing an external script that checks the health of
   * the node. An example script can be found at
   * <tt>src/main/sh/healthcheck/healthcheck.sh</tt> in the
   * <tt>hbase-examples</tt> module.
   */
  class HealthChecker {
  
    private static final Log LOG = LogFactory.getLog(HealthChecker.class);
    private ShellCommandExecutor shexec = null;
    private String exceptionStackTrace;
  
    /** Pattern used for searching in the output of the node health script */
    static private final String ERROR_PATTERN = "ERROR";
  
    private String healthCheckScript;
    private long scriptTimeout;
  
    enum HealthCheckerExitStatus {
      SUCCESS,
      TIMED_OUT,
      FAILED_WITH_EXIT_CODE,
      FAILED_WITH_EXCEPTION,
      FAILED
    }
  
    /**
     * Initialize.
     *
     * @param configuration
     */
    public void init(String location, long timeout) {
      this.healthCheckScript = location;
      this.scriptTimeout = timeout;
      ArrayList<String> execScript = new ArrayList<String>();
      execScript.add(healthCheckScript);
      this.shexec = new ShellCommandExecutor(execScript.toArray(new String[execScript.size()]), null,
          null, scriptTimeout);
      LOG.info("HealthChecker initialized with script at " + this.healthCheckScript +
        ", timeout=" + timeout);
    }
  
    public HealthReport checkHealth() {
      HealthCheckerExitStatus status = HealthCheckerExitStatus.SUCCESS;
      try {
        // Calling this execute leaves around running executor threads.
        shexec.execute();
      } catch (ExitCodeException e) {
        // ignore the exit code of the script
        LOG.warn("Caught exception : " + e + ",exit code:" + e.getExitCode());
        status = HealthCheckerExitStatus.FAILED_WITH_EXIT_CODE;
      } catch (IOException e) {
        LOG.warn("Caught exception : " + e);
        status = HealthCheckerExitStatus.FAILED_WITH_EXCEPTION;
        exceptionStackTrace = org.apache.hadoop.util.StringUtils.stringifyException(e);
      } finally {
        if (shexec.isTimedOut()) {
          status = HealthCheckerExitStatus.TIMED_OUT;
        }
        if (status == HealthCheckerExitStatus.SUCCESS) {
          if (hasErrors(shexec.getOutput())) {
            status = HealthCheckerExitStatus.FAILED;
          }
        }
      }
      return new HealthReport(status, getHealthReport(status));
    }
  
    private boolean hasErrors(String output) {
      String[] splits = output.split("\n");
      for (String split : splits) {
        if (split.startsWith(ERROR_PATTERN)) {
         return true;
       }
     }
     return false;
   }
 
   private String getHealthReport(HealthCheckerExitStatus status){
     String healthReport = null;
     switch (status) {
     case SUCCESS:
       healthReport = "Server is healthy.";
       break;
     case TIMED_OUT:
       healthReport = "Health script timed out";
       break;
     case FAILED_WITH_EXCEPTION:
       healthReport = exceptionStackTrace;
       break;
     case FAILED_WITH_EXIT_CODE:
       healthReport = "Health script failed with exit code.";
       break;
     case FAILED:
       healthReport = shexec.getOutput();
       break;
     }
     return healthReport;
   }
 }